I. Field of the Invention
This invention relates to the use of hydroxamic acid and hydroxamates for collecting toner particles from paper by a froth flotation process.
II. Description of the Prior Art
Froth flotation is regarded as one of the most efficient methods of removing ink particles from recycled mixed office waste. Flotation collectors such as tall oil often require the use of monovalent, divalent, or trivalent cations called "activators". The use of such activators makes the process difficult to control since activators incorporate bi- and multi- valent ions which not only contaminate but also prove to be deleterious to collector-fine particle interaction. Therefore it is necessary to maintain a proper balance between the amounts of collector and activator needed. The best solution is to have a collector that performs well in the absence of activators.
Use of hydroxamic acid, a chelating type collector, for removing impurities from kaolin is reported in U.S. Pat. No. 4,629,556 (Yoon, et al.). Yoon's process is used for the removal of colored titaniferous impurities from kaolin clay. Two major impurities in kaolin clay that can be removed by this process are anatase and iron oxides.
U.S. Pat. No. 3,438,494 discloses the use of alkyl or aryl substituted hydroxamic acids or salts thereof as collectors for chrysocolla (U.S. Pat. No. 3,438,494, Fuerstenan et al.).
Hydroxamic acid has been used as an inhibitor of urea decomposition (U.S. Pat. No. 3,920,015; Wortham). Hydroxamic acids have been used as sizing agents in paper formation (U.S. Pat. No. 4,857,149; Tiedeman et al.).
A large quantity of photocopied paper is discarded each year due to the lack of a satisfactory commercial process that can remove the toner particles from the pulp made from this paper. The toner particles are present in the paper made from this pulp which lowers the quality of the paper. These toner particles are hard to remove because the resin and the pigment are fused together onto the paper by the heat applied during the photocopying process.
None of the above references, however, discloses or suggests the use of hydroxamates as collectors for the flotation of toner particles on paper that is designed to be recycled.